The U.S. Marshals Service said Thursday it will auction roughly $18 million in bitcoins seized last fall from Silk Road, a website that was effectively the eBay of illegal drugs.

The marshals said Thursday that they will auction the virtual “coins,” consisting of sets of numbers entered in an online public ledger, via the Web on June 27.

Authorities say Silk Road generated more than $1 billion in illicit business from January 2011 to October 2013, when alleged operator Ross William Ulbricht was arrested in a public library in San Francisco. Ulbricht has pleaded not guilty. The website took commissions in bitcoins, which are hard to track.

The marshals are auctioning off 29,657 bitcoins in 10 blocks, which means buyers will need to pony up nearly $1.8 million each.